Python3 triggers an array error even tho i am not using an array. Probably my syntax is wrong but i do not...

Hi there i have written some code for my physics studys and i am fairly new to python.

Can someone explain to me why

[code]while s < 3.05 and t < 1e-7 :[/code]

triggers

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

i googled for quite a while and searched stack but i have no idea what the problem is.

edited Nov 19 '18 at 19:51

asked Nov 19 '18 at 19:26

Wölki

i do not think it is a duplicate because what i am using is not an array. For some reason Python thinks it is an array. Probably i did something wrong but i have no idea what
– Wölki
Nov 19 '18 at 19:50

that's ok if s and t are scalars. Look at s<3.05 alone. Does it make sense to apply a while or and to that result?
– hpaulj
Nov 19 '18 at 19:51

While s and t start off as scalars, something is change one or both into a numpy array. And as indicated in the duplicate, performing if, while and and operations on a boolean array doesn't work. You need to figure out, from the full error message. where the error occurs (which function), and figure out why s (or t) becomes an array (maybe dt is also an array, etc).
– hpaulj
Nov 19 '18 at 20:21

You are calling Ek with arrays. E is then an array. v is derived from that, as is ds. So on the next loop s+ds is also an array. Ek may work fine with scalar E and p, but it is not setup to work with arrays.
– hpaulj
Nov 19 '18 at 20:25

that is the problem. I have no idea what may cause this. File "/tmp/mozilla_woelki0/arrayerror.py", line 67, in Ek while s < 3.05 and t < 1e-7 : ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() This is everything i get as an error. I do not find where to get a grip at this. I highly appreciate you trying to help
– Wölki
Nov 19 '18 at 20:29

|
show 2 more comments

Hi there i have written some code for my physics studys and i am fairly new to python.

Can someone explain to me why

[code]while s < 3.05 and t < 1e-7 :[/code]

triggers

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

i googled for quite a while and searched stack but i have no idea what the problem is.

edited Nov 19 '18 at 19:51

asked Nov 19 '18 at 19:26

Wölki

i do not think it is a duplicate because what i am using is not an array. For some reason Python thinks it is an array. Probably i did something wrong but i have no idea what
– Wölki
Nov 19 '18 at 19:50

that's ok if s and t are scalars. Look at s<3.05 alone. Does it make sense to apply a while or and to that result?
– hpaulj
Nov 19 '18 at 19:51

While s and t start off as scalars, something is change one or both into a numpy array. And as indicated in the duplicate, performing if, while and and operations on a boolean array doesn't work. You need to figure out, from the full error message. where the error occurs (which function), and figure out why s (or t) becomes an array (maybe dt is also an array, etc).
– hpaulj
Nov 19 '18 at 20:21

You are calling Ek with arrays. E is then an array. v is derived from that, as is ds. So on the next loop s+ds is also an array. Ek may work fine with scalar E and p, but it is not setup to work with arrays.
– hpaulj
Nov 19 '18 at 20:25

that is the problem. I have no idea what may cause this. File "/tmp/mozilla_woelki0/arrayerror.py", line 67, in Ek while s < 3.05 and t < 1e-7 : ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() This is everything i get as an error. I do not find where to get a grip at this. I highly appreciate you trying to help
– Wölki
Nov 19 '18 at 20:29

|
show 2 more comments

Hi there i have written some code for my physics studys and i am fairly new to python.

Can someone explain to me why

[code]while s < 3.05 and t < 1e-7 :[/code]

triggers

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

i googled for quite a while and searched stack but i have no idea what the problem is.

edited Nov 19 '18 at 19:51

asked Nov 19 '18 at 19:26

Wölki

Hi there i have written some code for my physics studys and i am fairly new to python.

Can someone explain to me why

[code]while s < 3.05 and t < 1e-7 :[/code]

triggers

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

i googled for quite a while and searched stack but i have no idea what the problem is.

python-3.x numpy matplotlib

edited Nov 19 '18 at 19:51

asked Nov 19 '18 at 19:26

Wölki

edited Nov 19 '18 at 19:51

asked Nov 19 '18 at 19:26

Wölki

edited Nov 19 '18 at 19:51

asked Nov 19 '18 at 19:26

Wölki

asked Nov 19 '18 at 19:26

Wölki

asked Nov 19 '18 at 19:26

Wölki

i do not think it is a duplicate because what i am using is not an array. For some reason Python thinks it is an array. Probably i did something wrong but i have no idea what
– Wölki
Nov 19 '18 at 19:50

that's ok if s and t are scalars. Look at s<3.05 alone. Does it make sense to apply a while or and to that result?
– hpaulj
Nov 19 '18 at 19:51

While s and t start off as scalars, something is change one or both into a numpy array. And as indicated in the duplicate, performing if, while and and operations on a boolean array doesn't work. You need to figure out, from the full error message. where the error occurs (which function), and figure out why s (or t) becomes an array (maybe dt is also an array, etc).
– hpaulj
Nov 19 '18 at 20:21

You are calling Ek with arrays. E is then an array. v is derived from that, as is ds. So on the next loop s+ds is also an array. Ek may work fine with scalar E and p, but it is not setup to work with arrays.
– hpaulj
Nov 19 '18 at 20:25

that is the problem. I have no idea what may cause this. File "/tmp/mozilla_woelki0/arrayerror.py", line 67, in Ek while s < 3.05 and t < 1e-7 : ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() This is everything i get as an error. I do not find where to get a grip at this. I highly appreciate you trying to help
– Wölki
Nov 19 '18 at 20:29

|
show 2 more comments

i do not think it is a duplicate because what i am using is not an array. For some reason Python thinks it is an array. Probably i did something wrong but i have no idea what
– Wölki
Nov 19 '18 at 19:50

that's ok if s and t are scalars. Look at s<3.05 alone. Does it make sense to apply a while or and to that result?
– hpaulj
Nov 19 '18 at 19:51

While s and t start off as scalars, something is change one or both into a numpy array. And as indicated in the duplicate, performing if, while and and operations on a boolean array doesn't work. You need to figure out, from the full error message. where the error occurs (which function), and figure out why s (or t) becomes an array (maybe dt is also an array, etc).
– hpaulj
Nov 19 '18 at 20:21

You are calling Ek with arrays. E is then an array. v is derived from that, as is ds. So on the next loop s+ds is also an array. Ek may work fine with scalar E and p, but it is not setup to work with arrays.
– hpaulj
Nov 19 '18 at 20:25

that is the problem. I have no idea what may cause this. File "/tmp/mozilla_woelki0/arrayerror.py", line 67, in Ek while s < 3.05 and t < 1e-7 : ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() This is everything i get as an error. I do not find where to get a grip at this. I highly appreciate you trying to help
– Wölki
Nov 19 '18 at 20:29

i do not think it is a duplicate because what i am using is not an array. For some reason Python thinks it is an array. Probably i did something wrong but i have no idea what
– Wölki
Nov 19 '18 at 19:50

that's ok if s and t are scalars. Look at s<3.05 alone. Does it make sense to apply a while or and to that result?
– hpaulj
Nov 19 '18 at 19:51

While s and t start off as scalars, something is change one or both into a numpy array. And as indicated in the duplicate, performing if, while and and operations on a boolean array doesn't work. You need to figure out, from the full error message. where the error occurs (which function), and figure out why s (or t) becomes an array (maybe dt is also an array, etc).
– hpaulj
Nov 19 '18 at 20:21

You are calling Ek with arrays. E is then an array. v is derived from that, as is ds. So on the next loop s+ds is also an array. Ek may work fine with scalar E and p, but it is not setup to work with arrays.
– hpaulj
Nov 19 '18 at 20:25

that is the problem. I have no idea what may cause this. File "/tmp/mozilla_woelki0/arrayerror.py", line 67, in Ek while s < 3.05 and t < 1e-7 : ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() This is everything i get as an error. I do not find where to get a grip at this. I highly appreciate you trying to help
– Wölki
Nov 19 '18 at 20:29

|
show 2 more comments

1 Answer
1

active

oldest

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When I copy-n-paste the code if runs (thankfully) and produces the error message:

1231:~/mypy$ python3 stack53381357.py 

Traceback (most recent call last):

  File "stack53381357.py", line 105, in <module>

    Z = Ek(X, Y)

  File "stack53381357.py", line 67, in Ek

    while s < 3.05 and t < 1e-7 :

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Note that the full message does tell us where the problem is - in the Ek function at line 67. That is relevant information.

That confirms my comment - Ek is called with array arguments, and that propagates through the loop, changing s to an array.

When I add a print to the end of the Ek loop:

    print(type(s), s.shape)

I get, before the error:

<class 'numpy.ndarray'> (100, 100)

So, yes, s has changed from a scalar to a numpy array, the same shape as the X and Y arrays you passed to Ek.

Your 3 functions appear to have been written for scalar inputs. I'm not going to try to figure out how they should work with the meshgrid inputs. You could iterate over the pa and Ea elements. Or you could modify the functions so they do behave when given array values. At the very least the

while (s<3.05) and (t<1e-7):

has to be written to be meaningful when s is an array. There may be other problems with array inputs.

edited Nov 19 '18 at 20:45

answered Nov 19 '18 at 20:36

hpaulj

110k774141

add a comment |

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1 Answer
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When I copy-n-paste the code if runs (thankfully) and produces the error message:

1231:~/mypy$ python3 stack53381357.py 

Traceback (most recent call last):

  File "stack53381357.py", line 105, in <module>

    Z = Ek(X, Y)

  File "stack53381357.py", line 67, in Ek

    while s < 3.05 and t < 1e-7 :

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Note that the full message does tell us where the problem is - in the Ek function at line 67. That is relevant information.

That confirms my comment - Ek is called with array arguments, and that propagates through the loop, changing s to an array.

When I add a print to the end of the Ek loop:

    print(type(s), s.shape)

I get, before the error:

<class 'numpy.ndarray'> (100, 100)

So, yes, s has changed from a scalar to a numpy array, the same shape as the X and Y arrays you passed to Ek.

while (s<3.05) and (t<1e-7):

has to be written to be meaningful when s is an array. There may be other problems with array inputs.

edited Nov 19 '18 at 20:45

answered Nov 19 '18 at 20:36

hpaulj

110k774141

add a comment |

When I copy-n-paste the code if runs (thankfully) and produces the error message:

1231:~/mypy$ python3 stack53381357.py 

Traceback (most recent call last):

  File "stack53381357.py", line 105, in <module>

    Z = Ek(X, Y)

  File "stack53381357.py", line 67, in Ek

    while s < 3.05 and t < 1e-7 :

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Note that the full message does tell us where the problem is - in the Ek function at line 67. That is relevant information.

That confirms my comment - Ek is called with array arguments, and that propagates through the loop, changing s to an array.

When I add a print to the end of the Ek loop:

    print(type(s), s.shape)

I get, before the error:

<class 'numpy.ndarray'> (100, 100)

So, yes, s has changed from a scalar to a numpy array, the same shape as the X and Y arrays you passed to Ek.

while (s<3.05) and (t<1e-7):

has to be written to be meaningful when s is an array. There may be other problems with array inputs.

edited Nov 19 '18 at 20:45

answered Nov 19 '18 at 20:36

hpaulj

110k774141

add a comment |

When I copy-n-paste the code if runs (thankfully) and produces the error message:

1231:~/mypy$ python3 stack53381357.py 

Traceback (most recent call last):

  File "stack53381357.py", line 105, in <module>

    Z = Ek(X, Y)

  File "stack53381357.py", line 67, in Ek

    while s < 3.05 and t < 1e-7 :

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Note that the full message does tell us where the problem is - in the Ek function at line 67. That is relevant information.

That confirms my comment - Ek is called with array arguments, and that propagates through the loop, changing s to an array.

When I add a print to the end of the Ek loop:

    print(type(s), s.shape)

I get, before the error:

<class 'numpy.ndarray'> (100, 100)

So, yes, s has changed from a scalar to a numpy array, the same shape as the X and Y arrays you passed to Ek.

while (s<3.05) and (t<1e-7):

has to be written to be meaningful when s is an array. There may be other problems with array inputs.

edited Nov 19 '18 at 20:45

answered Nov 19 '18 at 20:36

hpaulj

110k774141

When I copy-n-paste the code if runs (thankfully) and produces the error message:

1231:~/mypy$ python3 stack53381357.py 

Traceback (most recent call last):

  File "stack53381357.py", line 105, in <module>

    Z = Ek(X, Y)

  File "stack53381357.py", line 67, in Ek

    while s < 3.05 and t < 1e-7 :

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Note that the full message does tell us where the problem is - in the Ek function at line 67. That is relevant information.

That confirms my comment - Ek is called with array arguments, and that propagates through the loop, changing s to an array.

When I add a print to the end of the Ek loop:

    print(type(s), s.shape)

I get, before the error:

<class 'numpy.ndarray'> (100, 100)

So, yes, s has changed from a scalar to a numpy array, the same shape as the X and Y arrays you passed to Ek.

while (s<3.05) and (t<1e-7):

has to be written to be meaningful when s is an array. There may be other problems with array inputs.

edited Nov 19 '18 at 20:45

answered Nov 19 '18 at 20:36

hpaulj

110k774141

edited Nov 19 '18 at 20:45

answered Nov 19 '18 at 20:36

hpaulj

110k774141

answered Nov 19 '18 at 20:36

hpaulj

110k774141

answered Nov 19 '18 at 20:36

hpaulj

110k774141

add a comment |

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